1. Field of the Invention
This invention relates to an electroluminescent device having excellent luminescence properties.
2. Description of the Related Art
An organic electroluminescent device (which will hereinafter be called xe2x80x9corganic EL devicexe2x80x9d) is a light-emitting device which makes use of the principle that when an electric field is applied, a fluorescent material emits light in response to the charge recombination of holes injected from an anode and electrons injected from a cathode.
After C. W. Tang et al. of Eastman Kodak Company reported a low-voltage-driven organic EL device using a double layered structure (C. W. Tang, S. A. Vanslyke, Applied Physics Letters, 51,913(1987) and the like), studies on an organic EL device have been briskly carried out. Tang et al. reported an organic EL device using tris(8-hydroxyquinolinol aluminum) in a light-emitting layer and a triphenyldiamine derivative to a hole-transporting layer. This stacked structure gives such advantages as an improvement in the injection efficiency of holes into the light-emitting layer; blocking of electrons injected from a cathode, which increase the efficiency of exciton production from charge recombination; and confinement of the excitons into the light-emitting layer. A double layered structure composed of a hole-injecting and transporting layer and an electron-transporting and light-emitting layer or a triple layered structure composed of a hole-injecting and transporting layer, a light-emitting layer and an electron-injecting and transporting layer is well known as an organic EL device. In order to increase the recombination efficiency of injected holes and electrons, various improvements in the device structure or fabrication process have been introduced to such multi-layered devices.
As a hole-transporting material, triphenylamine derivatives such as 4,4xe2x80x2,4xe2x80x3-tris(3-methylphenylphenylamino) triphenylamine and aromatic diamine derivatives such as N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-bis(3-methylphenyl)-[1,1xe2x80x2-biphenyl]-4,4xe2x80x2-diamine, which are starburst molecules, are well known (e.g., Japanese Patent Application Laid-Open Nos. 20771/1996, 40995/1996, 40997/1996, 53397/1996 and 87122/1996). As an electron-transporting material, oxadiazole derivatives, triazole derivatives and the like are well known.
As a light-emitting material, known are chelate complexes such as tris(8-quinolinolate)aluminum complex, coumarin derivatives, tetraphenylbutadiene derivatives, bisstyrylarylene derivatives, oxadiazole derivatives and the like. Since various color light in a visible region from blue to red are obtained from these light-emitting materials, there increased expectation for industrialization of a full color organic EL device (e.g., Japanese Patent Application Laid-Open Nos. 239655/1996, 138561/1995, 200289/1991 and the like). The pyrromethene-BF2 complexes are well known as a luminescent material (e.g., Japanese Patent Application Laid-Open Nos. 289081/1997).
In recent days, organic EL devices with high brightness and long lifetime have been disclosed or reported, but any of them are not enough in these properties.
An object of the present invention is to provide a material of high performance and to provide an organic EL device having high luminance.
The present inventors have repeated experiments. As a result, they have found that an organic EL device having superior emission properties is obtained by using particular perylene derivatives or pyrromethene-metal complexs as a luminescent material.
The present inventors have found that said materials has high carrier transporting properties and an organic EL device having superior emission properties is obtained by using said compounds as a hole-transporting material or electron-transporting material. The present inventors have found that an organic EL device having superior emission properties is obtained by using a mixture of said compounds and another hole or electron-transporting material.
In the present invention, there is thus provided an organic electroluminescent device comprising an anode, a cathode and one or more than one organic thin-film layers including a light-emitting layer between said anode and said cathode, wherein at least one of said organic thin-film layers contains, either singly or as a mixture, a perylene compound represented by the following formula (1): 
wherein R1 to R12 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted amino group, a nitro group, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted aryloxy group; and any two of R1 to R12 may form a ring; although at least one of R1 to R12 is a substituted amino group represented by the following formula (2): 
wherein R13 to R23 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted amino group (except diarylamino group), a nitro group, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxycarbonyl group, a substituted or unsubstituted styryl group, or a carboxyl group; and any two of R13 to R23 may form a ring; and R24 to R28 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted diarylamino group expressed by xe2x80x94NAr11Ar12 wherein Ar11 and Ar12 each independently represents substituted or unsubstituted aryl group having 6-20 carbon atoms, a nitro group, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxycarbonyl group or a carboxyl group; and any two of R24 to R28 may form a ring.
In the present invention, there is also thus provided an organic electroluminescent device comprising an anode, a cathode and one or more than one organic thin-film layers including a light-emitting layer between said anode and said cathode, wherein at least one of said organic thin-film layers contains, either singly or as a mixture, a pyrromethene-metal complex represented by the following formula (3): 
wherein M represents monovalent, divalent or trivalent metal ion; n is an integer of 1, 2 or 3; R1 to R7 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted amino group, a nitro group, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted styryl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxycarbonyl group or a carboxyl group; and any two of R1 to R7 may form a ring.
The organic EL device according to the present invention which contains a compound of formula (1) or (3) in an organic thin-film layer emits light with higher brightness compared with the conventional organic EL device.